1. Field of the Invention
The present invention relates to a vehicular drive system in which a motor and a power transmission mechanism are connected via motor isolation means, and the driving force of the motor is transmitted to driven wheels via the power transmission mechanism, the power transmission mechanism and the motor being lubricated with a common oil.
2. Description of the Related Art
In a drive system for an electric motor vehicle described in Japanese Patent Application Laid-open No. 9-226394, a motor chamber housing a motor and a gear chamber housing a gear section for transmitting the driving force of the motor to driven wheels are separated by a partition wall, which has an orifice providing communication between the gear chamber and the motor chamber. When the motor is running, oil splashed by a rotating gear within the gear chamber is supplied to the motor chamber, thus lowering the oil level in the gear chamber to reduce the oil stirring resistance to the gear.
In a hybrid vehicle equipped with an engine and a motor as drive sources for travel, if the motor is connected to a transmission when the vehicle travels at high speed using the driving force of the engine, there is the problem that the motor is dragged by the driving force of the engine, thus generating a frictional loss. Furthermore, since the oil retained within the transmission is stirred by a rotating gear when the vehicle is traveling, there is the problem that the stirring resistance causes an engine driving force loss which is particularly large when the engine is running at high speed.